The only human cathelicidin antimicrobial peptide with broad-spectrum activity against bacteria, viruses, and fungi.
Last Updated: May 2026
LL-37 is the only human cathelicidin antimicrobial peptide, a 37-amino-acid endogenous peptide derived from the hCAP18 precursor with broad-spectrum activity against bacteria, viruses, and fungi, plus extensive immunomodulatory effects on host cells. It is the most clinically-developed cathelicidin peptide and the focus of substantial research interest in antimicrobial resistance and immune dysregulation contexts. Important regulatory update: LL-37 was removed from the FDA's Category 2 bulk substances list on April 22, 2026 and is scheduled for PCAC review in early 2027.
LL-37 is the active form of the human cathelicidin antimicrobial peptide, cleaved from the hCAP18 precursor and expressed by neutrophils, epithelial cells, and other immune-relevant cell populations. It has multiple mechanisms: direct antimicrobial activity through membrane disruption of bacteria, viruses (including respiratory pathogens), and fungi; immune-modulatory effects including chemotactic signaling and inflammation regulation; and tissue-repair effects through epithelial cell migration and wound healing pathways. Evidence level: Preclinical extensive (antimicrobial, immune, wound healing); limited human clinical trials.
Preclinical studies have demonstrated broad antimicrobial activity, including against multidrug-resistant bacteria, immune-modulatory effects in chronic inflammatory conditions, and wound-healing acceleration in various injury models. Human clinical research has explored LL-37 derivatives in topical wound care, anti-inflammatory contexts, and antimicrobial applications. The native LL-37 sequence has been studied less in formal Phase 2/3 trials than engineered derivatives. Evidence level: Preclinical extensive; human clinical for derivatives more than native LL-37.
LL-37 is the human-genome-encoded antimicrobial peptide — distinguishing it from synthetic antimicrobial peptides developed as therapeutic candidates and from other immune-modulating compounds.
| Compound | Antimicrobial activity | Immune modulation | Origin |
|---|---|---|---|
| LL-37 | Broad-spectrum (bacteria, viruses, fungi) | Yes (chemotactic, anti-inflammatory) | Human cathelicidin (endogenous) |
| KPV | None | Yes (NF-κB inhibition) | α-MSH-derived |
| Thymosin Alpha-1 | Indirect (immune-mediated) | Yes (T-cell modulation) | Thymic peptide |
LL-37 administration can produce mild injection-site reactions and, at higher doses, mast cell degranulation effects (transient histamine-mediated symptoms). As an endogenous peptide, LL-37 has favorable inherent safety, but high-dose administration may produce dose-related inflammatory effects through its own immune-modulatory mechanism. Long-term safety at sustained research-use dosing is not well-characterized in human RCT. Evidence level: Preclinical safety; human safety from derivatives studies; long-term unestablished.
LL-37 is not approved for any medical indication anywhere in the world as of May 2026. On April 22, 2026, LL-37 was removed from the FDA's Category 2 bulk substances list and is scheduled for Pharmacy Compounding Advisory Committee (PCAC) review in early 2027. Removal from Category 2 does not authorize compounding pharmacy production — formal Category 1 inclusion or 503A bulks list addition remains pending PCAC determination. Current status in FDA peptide regulation 2025–2026 timeline.
LL-37's 37-amino-acid length makes synthesis quality control more variable than for shorter peptides, and the cationic amphipathic structure can lead to misfolding or aggregation issues that affect activity. Independent HPLC purity testing and mass spectrometry identity confirmation are essential. Endotoxin testing is particularly important given the immune-modulatory mechanism. Guidance in how-to-test-peptides hub.
Peptigrity purchases LL-37 vials anonymously at standard customer pricing, sends them to ISO-accredited third-party labs for HPLC, mass spectrometry, and endotoxin analysis, and publishes the unedited certificate of analysis. Methodology in how we calculate trust scores.
LL-37 is the only human cathelicidin antimicrobial peptide, with broad-spectrum activity against bacteria, viruses, and fungi, plus extensive immune-modulatory and wound-healing effects. Preclinical evidence is substantial; human clinical evidence is more developed for engineered derivatives than for native LL-37.
LL-37 is legal to purchase as a research chemical for laboratory use in most jurisdictions, but it is not approved for human consumption. The April 22, 2026 Category 2 removal opens a potential future compounding pathway pending PCAC review in early 2027. Country breakdown in peptide legal status guide.
LL-37 is scheduled for Pharmacy Compounding Advisory Committee (PCAC) review in early 2027. Removal from Category 2 in April 2026 was a procedural step; formal authorization for compounding pharmacy production remains pending PCAC determination. Track developments in FDA peptide regulation 2025–2026 timeline.
Preclinical evidence has demonstrated LL-37 activity against multidrug-resistant bacteria including MRSA and other antibiotic-resistant pathogens, with the membrane-disruption mechanism less prone to traditional resistance pathways. Human clinical evidence for antimicrobial resistance applications is more limited.
Independent third-party HPLC certificate of analysis from a lab the vendor does not own or pay, with mass spectrometry identity confirmation and endotoxin testing. The 37-amino-acid length makes purity verification more important than for shorter peptides. COA interpretation in red flags in peptide certificates of analysis.
No. LL-37 is not approved for human consumption and Peptigrity is an independent review platform, not a medical authority. Research-use dosing varies widely. Anyone considering use should consult a licensed physician.
This section is for educational and informational purposes only and does not constitute medical advice. LL-37 is not approved by the FDA or any major Western regulator for human use, though it was removed from Category 2 of the FDA 503A bulk substances list in April 2026 and is scheduled for PCAC review in early 2027. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.
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